This invention concerns a utility mine scoop machine with mine dusting capability, particularly for use in coal mines. The dusting aspect of the scoop can more effectively provide low levels of dust, e.g., limestone dust, of uniform densities or solids concentrations to the mine ventilation air currents for transportation thereby over substantial distances.
In underground coal mines, large amounts of coal dust are necessarily generated by the cutting, blasting, loading, crushing and the like of the coal. This dust not only is present in high concentrations at these sites but is carried by the mine ventilation air current from these sites, as well as from belt conveyor transfer point and locations along the belt conveyor where ventilation checks are installed, throughout the mines until it settles out on down stream surfaces. Such atmospheric dust, and settled-out dust accumulations are fire and explosion hazards and must be periodically cleaned up or made inert by addition of limestone rock dust.
There are several ways in which underground coal mines generate coal dust, (1) when the coal is cut from the coal seam, (2) when the coal is loaded into equipment that takes the coal to a feeder, (3) when the feeder crushes the coal, (4) when the feeder discharges the coal onto a conveyor belt and, (5) when the coal is discharged from one conveyor belt to the next conveyor belt.
This coal dust is carried by the ventilating air stream into the return ventilation air entries where it settles out in these entries and along the conveyor belt. The dust is also carried along the belt conveyor entries by the air stream in these entries.
Federal law requires that intake entries be 65% inert, and that return entries be 80% inert. Limestone dust is spread in the intake and return entries to get the needed percentages of inertness.
Federal law also does not allow coal dust to remain on top of surfaces underground. For example, an entry could have the percent inertness required but if coal dust is on top of the limestone dust and the entry is black with coal dust, a violation of federal law could be cited.
To keep the return entries and belt conveyor entries white, a limestone distributor called a Trickle Duster is typically employed as shown in U.S. Pat. No. 4,872,598 the disclosure of which is hereby incorporated herein by reference in it entirety. These dusters have an air blower and a tank that holds limestone (rock) dust. The blower discharge air goes into the tank typically up thru the limestone dust and fluidizes the dust. A small portion of the limestone dust is carried by the air stream and is continuously discharged into the entries. The trickle duster discharges a continuous fog of limestone dust that is carried by the ventilation air and helps to keep the return entries and conveyor belt entries white.
With reference to an alternative embodiment of trickle duster, anytime air is taken underground and is warmer than the underground ambient temperature (normally 50-55° F.), a condition of 100% humidity or so is present. In summer months, all surfaces in an underground coal mine are wet. The air that is blown into the limestone dust is at about 100% humidity and the limestone dust absorbs water during its fluidization which causes particles of the dust to become heavier and to stick together. When this limestone dust is discharged into the air stream entries, it will not travel as far and will not uniformly coat surfaces within the mine because it is wet and particles of the dust have agglomerated.
In one preferred embodiment of the present invention, the duster structure is shown in FIG. 1 in cross-section and delivers limestone dust and pressurized air to the mine entries rapidly whereby the dust will only be exposed to the high humidity air from the ambient air from a blower for a short period of time in the delivery hose as compared to prior dusters which are designed to form dust-in-air suspensions within the dust feed hopper apparatus. Employing this duster, limestone dust will travel a greater distance in the entries since it is dry and particles of dust will not be stuck together. This preferred duster employs an auger in the bottom of a vee bottom tank, an air blower and preferably with the addition of a vibrator on at least one sloped side wall to aide in dust movement to the auger and specially designed dust discharge structure which produces a substantially dry dust-in-air discharge stream. By mounting the duster on a battery powered scoop such as shown in FIGS. 5-7, the duster can be transported within the mine, e.g., wherein the mine shaft is only 2 or 3 feet high, by commonly used scoop equipment to any location that the scoop equipment can go. This feature allows for total dust penetration throughout the mine. The motorized structure of the duster preferably is battery operated but can use any power source. Other commonly used dusters can be used, but the one shown in FIG. 1 is preferred.